Apparently, criminals there steal license plates and put them on their cars to avoid getting caught after they've stolen gas, according to a report in the Des Moines Register.

But even with these new approaches to stealing, overall gasoline theft is down.

In 2005, $300 million of gasoline was stolen nationally, according to the Association for Convenience and Petroleum Retailing.

The following year, that number plummeted to $122 million.

The reason: Gas stations have cut back on letting people pump first and pay later.

"For years, the last thing you wanted to do was make your cash customers go inside the store twice. They buy less, they get pissed off … and they can pay by credit card, which is the last thing you want them to do," Lenard said. "But what happened is, we had $3 gas in 2005. We had $3 gas in 2006. People just kept on stealing and [retailers] said, 'That's it, I'm locking down the pumps.'"

Lenard said stores really started to crack down after Hurricane Katrina, and it now seems like a permanent shift.

"The psychology is, if you go inside before and prepay, you're less likely to go back inside the store and buy a soda. But if you go inside after you fill up, you're more likely to buy something," he said.

Customers who are forced to prepay, he said, "buy less gas because you don't want to schlep inside and get change. So if you're not sure if it's $30 or $40, you'll do $30."